Microfluidic devices and systems have been gaining substantial interest as they are increasingly being demonstrated to be robust, highly accurate, high throughput and low cost methods of performing previously cumbersome and or expensive analytical operations.
In particular, microfluidic systems have been described for use in ultra high throughput screening assay systems, e.g., for pharmaceutical discovery, diagnostics and the like. See PCT Publication No. WO 98/00231, published Jan. 8, 1998. In addition, such microfluidic systems have reportedly been used in performing separations-based analyses, e.g., nucleic acid separations, etc. See, e.g., Woolley et al., Proc. Nat'l Acad. Sci., U.S.A. 91:11348-11352 (1994).
Despite the promise of microfluidic systems in terms of throughput, automatability and cost, many of the systems that have been described suffer from substantial drawbacks. Initially, many of these systems have substantial reductions in resolution over their counterpart methods on the bench top. In particular, a number of relatively minor considerations can readily become major factors when considered in the context of the relatively small amounts of material transported through these systems. For example, in microfluidic channels that include curves or turns, variations in distances through these turns and curves at the inside and outside edges can substantially affect the resolution of materials transported through these channels.
Further, simple operations, such as dilution and mixing have generally been accomplished at the expense of overall device volume, e.g., adding to the reagent/material volume required for carrying out the overall function of the device. In particular, such mixing typically requires much larger chambers or channels in order to provide adequate mixing of reagents or diluents within the confines of the microfluidic systems.
Thus, it would be generally desirable to provide microfluidic systems that are capable of capitalizing upon the myriad benefits described above, without sacrificing other attributes, such as resolution, volume, and the like. The present invention meets these and other needs.